Hoisting winch, in particular for a boring machine

ABSTRACT

For hoisting a load and allowing the load to fall freely. The device comprises a rotatable drum around which a cable for attaching to the load is wound. A hydraulic drive motor is permanently coupled with the drum and comprises a stator and a rotor rotated by application of a main fluid pressure and capable of being rendered freely rotative relative to the stator by application of an auxiliary control fluid pressure. A fluid supply device is adapted to supply in an alternating manner the main fluid pressure for raising the load and the auxiliary control pressure for allowing the load to fall freely.

United States Patent [191 Cassez et al. v

[451 July 22, 1975 3,283,668 ll/l966 HOISTING WINCH, IN PARTICULAR FOR ABORING MACHINE Inventors: Pierre Cassez, Bethune; Claude Pelisson,Seclin, both of France Assignee: Benoto-Sam, Paris, France Filed: Oct.3, 1973 Appl. No.: 403,004

Foreign Application Priority Data Oct. 3, 1972 France 72.3495] [1.8. CI254/150 FR; 91/44 Int. Cl. 866d 1/30 Field of Search 254/150 FH; 91/44UP References Cited UNITED STATES PATENTS Louhio 91/44 3.776513 l2/l973Mosley 254/150 FH Primary ExaminerRobert B. Reeves AssistantE.\'aminerHadd Lane Attorney. Agent. or Firm- Holman & Stern [57]ABSTRACT For hoisting a load and allowing the load to fall freely. Thedevice comprises a rotatable drum around which a cable for attaching tothe load is wound. A hydraulic drive motor is permanently coupled withthe drum and comprises a stator and a rotor rotated by application of amain fluid pressure and capable of being rendered freely rotativerelative to the stator by application of an auxiliary control fluidpressure. A fluid supply device is adapted to supply in an alternatingmanner the main fluid pressure for raising the load and the auxiliarycontrol pressure for allowing the load to fall freely.

16 Claims, 5 Drawing Figures PATENTED JUL 2 2 1975 SI iEET PATENTEDJUL22 I975 SHEET HOISTING WINCH, IN PARTICULAR FOR A BORING MACHINE Thepresent invention relates to hoisting winches and more particularly tohoisting winches whereby it is possible to hoist a load and allow theload to fall freely. Such winches are employed in boring machines whichcomprise a grab bucket of the percussion or hammer type which produces abored hole by successive impacts on the bottom of the hole and bysuccessive discharges of material which is broken up by the impacts ofthe bucket. The bucket thereafter brings the material to the surface ofthe ground.

The fact that the load of such a winch must be capable of falling freelywhich produces a considerable acceleration of the winch implies that thewinch cannot be directly coupled to the drive motor. Up to the presenttime this problem has been solved by providing between the winch and thedrive motor a clutch device which allows the shaft of the winch torotate freely as the load falls freely. However, this solution has thedrawback of the use of a clutch device which is difficult to regulateand subject to wear.

Moreover, often in the use of such a winch it is desirable to arrangethat the load does not fall completely freely and that the operator ofthe winch be capable of controlling the speed of the load in the courseof its descent. This has been rendered possible in the past by providinga brake device coupled with the winch shaft. However, this brake devicecreates an additional difficulty in the construction of the winch inthat it is necessary to co-ordinate with precision the operation of thebrake device and the operation of the clutch device which presentsnumerous problems.

An object of the invention is to provide a hoisting winch of the typeindicated hereinbefore which avoids use of a mechanical clutch devicebetween the drive motor and the winch shaft and which consequentlyfacilitates the co-ordination of the various operations to be carriedout.

The invention provides a winch for hoisting a load and allowing the loadto fall freely and comprising a rotatably mounted drum around which druma traction cable is wound, the cable being attached to the load, and adrive motor for driving the winch, wherein said motor is permanentlycoupled to the drum and comprises a hydraulic motor whose rotor iscapable of rotating freely with respect to the stator, that is to say,is capable of free-wheeling with respect to the stator, upon applicationof an auxiliary control pressure, said winch further comprising a supplydevice adapted to supply in an alternating manner a main pressure foroperating the motor for raising the load and the auxiliary controlpressure for the free fall of this load.

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawings.

In the drawings:

FIG. I is a diagrammatic side elevational view of a boring machinecomprising a percussion grab-bucket in which there is employed ahoisting winch according to the invention;

FIG. 2 is a partial elevational view, partly in section, of a winchaccording to the invention;

FIG. 3 is a side elevational view, with parts cut away, of the winchshown in FIG. 2;

FIG. 4 is a hydraulic diagram of the winch according to the invention,and

FIG. 5 shows a perspective diagrammatic view of a hydraulic motor usedfor the winch of FIG. 2-4.

The winch according to the invention permits raising a load and allowingthe load to fall freely with possibility of a regulation of its speed ofdescent. Such winches are employed in particular in boring machinesemploying a bucket or boring bit, in dredging machines for driving thebucket, in machines for cutting trenches by means of a bucket or boringbit, or like machines.

The ensuing description will apply to a boring machine employing abucket of the percussion or hammer type, but it must be understood thatthe invention is not intended to be limited to this particularapplication.

With reference to FIG. 1, it can be seen that the boring machinecomprises a vertical boring column A retained by guys B to a chassis Cwhich may be mobile or stationary. Mounted on the chassis C is aninternal combustion engine D and a hoisting winch E according to theinvention which drives, through a cable F, the bucket in its up and downmovement between the top G of the column A and the bottom of the boredhole. Note that in FIG. 1 the bucket is not visible and that the boringmachine is only represented diagrammatically since it does not form partof the invention.

With reference now more particularly to FIGS. 2 and 3, the mechanicalparts of the winch will first be described.

This winch is mounted on a base I from which vertically extend twosupports 2 and 3. Mounted in these supports is a drum 4 which is adaptedto receive a cable F shown in FIG. I and is rotatable about an axis XX.The drum 4 comprises a cylinder 5 having at one end an attached endflange 6 secured to a housing 7 of a hydraulic motor 8. The stator 9 ofthe motor 8 is located inside the rotor and secured to the support 2 soas to be prevented from rotating.

The cylinder 5 has at the end thereof opposed to the flange 6 an endwall 10 to which a wheel 11 is connected to rotate with the wall 10, thewheel having on its periphery a cylindrical braking surface 12 withwhich co-operates a brake band 13. The wall 10 is integral with ajournal 14 supported in a bearing 15 which is mounted in the support 3.A protection disc 16 is provided and defines one end of the surface onwhich the cable F may be wound around the drum 4.

The brake band 13 is secured at one end to a tensioning device 17 (FIG.3) which is pivoted at 18 to the base 1 of the winch. The other end ofthe brake band 13 is pivoted to an arm 19 which is integral with a lever20, the assembly comprising the arm 19 and the lever 20 being rotatableabout a pivot 21 which is integral with the base 1 of the winch. Thefree end of the lever 20 is connected to a rod 22 of a cylinder device23 whose cylinder is pivoted at 24 to the base 1. Inter-v posed betweenthe piston 25 of the cylinder device 23 and the end cap 26 of the latteris a spring 27 which acts on the lever 20in such manner that when thecylinder device 23 is not connected to a source of pressure, the brakeband 16 is applied against the peripheral surface 12 of the wheel 11 andthe brake device is in its applied position.

The hydraulic motor 8 is of the reversible type, its rotor and itsstator being rotatable with respect to each other by application of themain hydraulic pressure so as to produce a driving torque. Moreover, therotor and the stator are rotatable with respect to each othersubstantially without friction and at very high speed upon cessation ofthe main hydraulic pressure and application of a command pressure whichproduces of course no torque. A motor of this type which is particularlyappropriate for the winch according to the invention is thatmanufactured and sold by the Swedish firm Hagglunds under reference N4150 and whose main hydraulic output is 4.71 litres/revolution. Such amotor comprises (FIG. 5) a stator H in which are movable radial pistonsl subjected to the main pressure. Rotatable about this stator is a rotorK which is provided with a ring L having cams M. Rollers N integral withthe pistons I undergo a radial to-and-fro movement while being incontact with the cam ring L. In the course of operation of the motor,the main pressure applied to the pistons l urges the rollers N to remainconstantly in contact with the cam ring L of the rotor K so as to impartthereto a movement of rotation.

This motor also has a control port 80, which, when it is subjected to asecond given auxiliary control pressure, causes the radial pistons I tomove toward the axis Y Y of the motor and separates the rollers N fromthe cam ring L. Under these conditions, the rotor K of the motorfree-wheels with respect to the stator H, the frictional forces beingextremely low and resulting exclusively from the bearings of the motor.

Although this motor may be particularly appropriate for association withthe winch according to the invention it is possible to employ otherreversible hydraulic motors. For example, there may be employed themotor CH 800 sold by the firm Tractel. This motor comprises axialpistonswhich act on a moving plate, the pistons being capable of beingseparated from the plate so as to render the rotor freely rotatable withrespect to the stator.

The winch is associated with a control device whose preferredconstruction is shown in FIG. 4. The latter shows diagrammatically thehydraulic motor 8 shown in FIG. 2 and the flow ports 8a and 8b to whichthe main pressure is applied and the control or command port 8c whichreceives the control or command pressure for rendering the rotor Kfreely rotatable with respect to the stator H. In FIG. 4, there is alsoshown diagrammatically the cylinder device 23 and the brake band 13acting on the wheel 11.

The reversible hydraulic motor 8 is supplied by a pump unit 28comprising two pumps 29 and 30 having respectively a high output flowand a low output flow. These pumps 29 and 30 draw in the hydraulic fluidfrom a tank 31 through the filter-32.

The presence of the two pumps 29 and 30 enables the motor 8 to be drivenat different speeds. The pump 30 is connected to a pipe 33 which isconnected through a back-pressure valve 34 to a control directionalvalve 35 having five ports a to e. This valve can occupy three positionsthe intermediate position of which is the stable position shown in FIG.4. In this position, the backpressure valve 34 is connected to a pipe 36which is connected to a pipe 37 constituting the main return circuit ofthe hydraulic fluid. This pipe opens into the tank 31 through aback-pressure valve 38. The valve 35 may be put into the other positionsmanually. Thus the port a of the valve 35 may be put in communicationwith a pipe 39 which is directly connected to the port 8a of the motor8. The port a is also connected to the safety valve 34 connected to theport I) of the valve 35. The pipe 39 is connected to the port c and thepipe 36 is connected to the port d. Moreover, the valve 35 has a port ewhich is connected to a pipe 40 leading directly to the tank 31.

The motor 8 can be supplied with fluid by the pump 30 when the valve 35is placed in the position in which the ports a and c are connected toeach other.

Connected to the circuit just described is a supply circuit to which thepump 29 delivers fluid at a high rate of flow. The pump 29 is connectedto a pipe 41 which leads to a second directional valve 42 having fourports a, b, c and d. It is by means of this valve 42 that the pipe 41may be put in communication with the back-pressure valve 34 when theport a and the port c are manually connected to each other. However, thevalve 42 normally occupies the position shown in FIG. 4 in which theports 12 and d are in communication with each other so that in itsposition of rest the valve 42 allows the pump 29 to deliver fluiddirectly to the return pipe 37 through a pipe 43. On the other hand,putting the ports a and c of this valve in communication with each otherconnects the two supply circuits of the motor 8 in series relation.Consequently, the motor 8 can be connected first to the low-flow pump 30so as to obtain a low speed of the motor and thereafter to the pump 29whose flow is added to that of the pump 30 which results in a high speedrotation of the winch.

The pumps 29 and 30 are shown connected to the return pipe 37 throughsafety valves 44 and 45 which are calibrated or set at pressures whichhave been calculated in accordance with the pressures furnished by thepumps so as to put them in short-circuit when the set pressures arereached.

The port 8b of the motor 8 is normally connected through a pipe 46 to aback-pressure valve 47 which is also connected to the pipe 37. The pipe46 is connected to a three-way valve 48 to which a pipe 49 subjected tothe output pressure of the pump 29 is connected. One way of the valve 48is connected to a check valve 50 connected to the pipe 39.

The cylinder device 23 can receive a control pressure from a cylinderdevice-pilot valve 51 for releasing the brake controlled by a lever 52accessible to the operator. This connection is established through aselector 53 having three ports a, b and c, the port 0 being connected tothe pipe 39. The cylinder device-pilot valve 51 is connected directly tothe control port of the hydraulic motor 8 through a pipe 54 to which theoutlet of an accumulator 55 is also connected. The pipe 54 is connectedto the tank through a return pipe 56 in which is inserted a valve 57 setor calibrated to open at a predetermined pressure.

The selector 53 is connected through a pipe 58 to a control port a of apiloted check valve 59 connected to the tank 31 and to the safety valves44 and 45. The latter are each provided with control ports a throughwhich a control or command pressure may be applied so as to suppress thepressure setting of the valve. Note that a check valve 60 is insertedbetween thecheck valve 59 and the control port a of the safety valve 44.

The pipes 37 and 36 are connected to each other through a restriction 61and a check valve 62 connected in series.

The hoisting winch just described operates in the following manner:

It will be first recalled that when the winch is employed in a boringmachine such as that shown diagrammatically in FIG. 1, the reversiblehydraulic motor 8 must effect three distinct operations:

I. Raise the filled bucket.

2. Allow the bucket to fall freely or with a controlled braking thereof.

3. Unwind the cable F from the drum 4 when the bucket is not hooked tothe cable F.

When the boring machine is at rest, the brake band 13 is applied againstthe braking surface of the wheel 11 so as to prevent the winch fromrotating, the braking force applied to the band 13 being determinedsolely by the tension of the spring 27 placed in the cylinder device 23.By means of this arrangement, the machine is completely safe inoperation. If the hydraulic pressure applied to the cylinder device 23disappears, for example owing to a broken pipe, rotation of the winch isimmediately stopped.

The valve 335 permits a progressive control of the rate of flow ofhydraulic fluid therethrough and therefore controls the speed of themotor 8, that is to say the speed of the load.

Owing to the presence of the valves 35 and 42 and the pumps 30 and 29associated therewith, the motor 8 can rotate at two speeds. The higherspeed serves to furnish a normal hoisting force for hoisting the bucketand the lower speed permits applying to the traction cable F a higherhoisting force which may be necessary for extracting a bucket subjectedto the suction effect in the bored hole, or for de-blocking a boringtool, or for carrying out auxiliary operations. The two hoisting forcesare determined by the different calibrations or settings of the safetyvalves 44 and 45.

In order to facilitate the description of the operation of this winch,there will now be examined in turn:

1. The hoisting of the load.

2. The automatic free-wheeling of the hydraulic motor 8.

3. The automatic or manual release of the brake 13.

4. The safety device precluding an accidental hoisting command duringthe free-wheeling of the motor 8.

5. The unwinding of the cable F from the drum in the absence of a load.

The operation of this winch will be described with the use of certainpressure values which are imposed by the utilization of theaforementioned Hagglunds hydraulic motor. It will be understood thatthese values are given merely by way of example and that the inventionis not intended to be limited to the indicated values of pressure or toa hydraulic motor of a given type provided that it is possible to makethe stator free-wheel with respect to the motor, as explainedhereinbefore.

l. The hoisting of a load This operation is controlled manually by theoperator who acts on the valves 35 and 42, the valve 35 being actuatedfirst so that the valve 42 can become opera tive.

When the valve 35 is actuated so as to interconnect its ports a and c,the output flow from the pump 30 is applied to the pipe 39 andconsequently to the inlet port 80 of the motor, the return being throughthe valve 47, the pipe 37 and the valve 38.

When the valve 42 is actuated, the output flow from the pump 29 is addedto that from the pump 30 in passing through the pipe 41 and the ports aand c of the valve 35. Otherwise, the flow from the pump 29 is returneddirectly to the tank through the pipe 37. In the course of the rising ofthe load, the brake 13 is automatically released since the selector 53interconnects its ports b and c and therefore applies the main pressureof the motor to the cylinder device 23.

When the command from the valve 35 and 42 ceases, the circuit isimmediately in the condition for the free fall of the load which ishowever prevented by the action of the brake 13. Under these conditions,the motor 8 is free-wheeling.

2. The automatic freewheeling of the motor 8 As already mentioned, thisfree-wheeling is achieved by applying to the motor 8 an auxiliarycontrol or command pressure through its port 80. In the presentlydescribed embodiment, the minimum pressure for freewheeling (the releaseof the rollers N of the stator H from the cam ring L of the rotor K) isabout 0.6 kilogram/sq.cm whereas the maximum pressure allowed by thestrength of the housing of the motor 8 is l kg/sq.cm. The oil requiredfor this free-wheeling is supplied simultaneously by:

a. the accumulator 55 under a pressure of 0.5 kg/sq.cm which immediatelyreturns its volume of oil stored in accordance with the pressure of thecircuit which is' preferably 0.750 kg/sq.cm;

b. the pressurizing circuit supplied by way of the restriction 61 for asmall part. This motor housing pressurizing circuit comprises:

the valve 57 set at about 0.750 kg/sq.cm and em ployed as pressurelimiter;

the check valve 62 which maintains the pressure in the circuit uponstoppage of the machine and the pump unit 28;

a supply of the cylinder device-pilot valve 51 for permanentlypressurizing the manual brake release circuit for the brake 13.

This pressurizing circuit, which is constantly under pressure, maintainsthe motor constantly in a freewheeling condition in the absence of othercommands given by the operator. Thus the motor is always ready to permita free fall of the load.

Note also that in the main return pipe 37 the backpressure valve 38ensures an additional pressure drop by its calibration or setting so asto obtain a pressure of l kg/sq.cm at the inlet of the restriction 61.

Moreover, in order that the free wheeling of the motor 8 be achieved asdescribed hereinbefore, it is essential that the supply ports 8a and 8bof the motor be connected to the tank 31 or at a very low pressure. Thiscondition is achieved by:

l. The valve 35 which connects the port 8a of the motor to the tank 31is in position of rest shown in FIG. 4.

2. The check valve 50 which connects the port 8b of the motor to thepipe 40. As the setting of the valve 50 is 0.050 kg/sq.cm there remainsonly a very low pressure at the port 8b. Without this valve, the port 8bwould be under a retained pressure (2 kg/sq.cm) produced by the valve 47and the free-wheeling of the motor could not be suitably achieved.

In the hydraulic motor of the present embodiment, this means that onehalf of the pistons I of the stator H remains extended at the end of thehoisting or at the start of the free fall of the load, as soon as thebrake is released.

Now, the fact of entirely withdrawing the pistons I at the start of thefree fall by application of the auxiliary pressure to the port 8c on onehand and by the suppression of the main pressure at the ports 8a and 8bof the motor on the other, precludes tapping of the rollers N againstthe cam ring L of the rotor K. Note that the fact of having fullywithdrawn the pistons l at the start of the free fall precludes tappingof the rollers N against the cam ring L'of the housing.

When the winch has been stopped at the end of the hoisting, a very briefunwinding of the cable F occurs which is produced by the response timeof the brake 1 band 13 which has for effect to move the pistons l awayfrom thecam ring L.

The accumulator 55 performs a second function.

When the hoisting is commanded through the valve 35, the pistons l ofthe motor extend and bear against the cam ring L at the speedcorresponding to the flow of the oil supply. The accumulator thenabsorbs the volume of oil delivered from the housing of the motor whichis equal to the output volume of the pistons l with a variation inpressure which does not exceed the maximum allowed pressure of lkg/sq.cm. Simultaneously, the valve 57 discharges to the tank 31 so asto re-establish the normal pressure of the circuit (0.750 kg/sq.cm).

Itsaction alone, without the accumulator 55, would produce aninstantaneous pressure rise upon extension of the pistons.

3. Release of the brake band 13 The brake band is released eithermanually or automatically. The latter case has already been examined.

The double control or command is effected by the selector 53. Dependingon the force applied to the control lever 52 of the cylinder device 51,a pressure is established in the cylinder device 23 which reduces orcompletely cancels out the force of the spring 27. This variablehydraulic action brought about by the operator permits achieving avariable hydraulic pull on the brake band and affords a very sensitiveprogressivity in the braking. For the free fall, the operator acts inthe manner described hereinbefore by utilizing the complete travel ofthe cylinder device 51 so as to transmit the pressure and volume of theoil to the cylinder device 23 and compress the spring 27. Thecompression of the spring completely releases the brake band 13 andcauses the free fall of the load.

The automatic release when hoisting the load is achieved upon actuationof the valve 35 which puts the brake releasing circuit under pressurethrough the port of ,the selector 53 and supplies fluid to the cylinderdevice which compresses the spring 27 and releases the brake band 13.

In both cases, the spring 27 immediately resumes its braking action assoon as the hydraulic pressure in the cylinder device 23 is released.The selector 53 indeed permits the decompression and return of the oilfrom the port b to the port a in the first case and from the port b tothe port 0 in the second case.

This brake device has two main advantages, namely the progressivity andthe sensitivity in the manual release of the braking with possibility ofallowing the free fall of the load and the safety of operation by brakeaction in the case of breakage of a hydraulic pipe.

4. Safety device precluding an accidental actuation for hoisting duringthe free-wheeling of the motor 8 It is clear that during the free fallof the load it is absolutely necessary to avoid a coupling between therotor K and the stator H. indeed, bearing in mind the relatively highspeed of rotation between the rotor and the stator, which may be of theorder of 10 times higher than the normal speed of operation, the motorwould be immediately destroyed.

In the presently-described case of the Hagglands motor, the speed in thefree falling of the load may reach 500600 rpm whereas the normal speedis 70 rpm.

Moreover, in the case of the free fall of the load, the motor would actas a hydraulic pump and the high speed would produce the continuouspercussion of the rollers N against the cam ring L without possibilityof a coupling of the rotor K and stator l-l since the supply of oilwould be very distinctly insufficient and the inertia of the movingparts would be excessive.

Consequently, the safety device comprises the pipe 58 which connects theoutlet of the cylinder devicepilot valve 51 to the control port a of thepiloted valve 59, the check valve 60 and the back-pressure valve 34.

Putting the brake release circuit under pressure by actuation of thecylinder device-pilot valve 51 opens the valve 59 and this puts theports a which suppress the set pressure of the safety valves 44 and 45in communication with the tank 31. Consequently, these valves becomedischarge valves for the pumps 29 and 30 which then deliver fluiddirectly to the tank through the respective discharge ports.

However, there is a residual pressure upstream of the safety valves 44and 45 due to the internal pressure drops (in the present case 3.5kg/sq.cm), which may supply the valve 35. The back-pressure valve 34,which is set at 5 kg/sq.cm, precludes this supply and the valve 35 maybe actuated without incident, even in the course of the free fall of theload.

When there is no brake release order, the piloted valve 59 is normallyclosed and permits the operation of the safety valves at the desiredpressure settings. For this operation, the valve 60 isolates theinternal piloting circuits of the safety valves 44 and 45 by avoidingthe discharge from the valve 45 to the valve 44.

5. Unwinding of the cable F from the drum in the absence of load Theunwinding of the drum by a reversal of the direction of rotation of thehydraulic motor 8 avoids manually pulling on the cable to achieve areverse rotation.

Actuation of the three-way valve 48 interconnects through its ports band c the delivery side of the pump 29 and the outlet 8b of thehydraulic motor 8. By manually releasing the brake band 13 by means ofthe cylinder device 51 and actuating the valve 42, the residual pressureat the safety valves 44 and 45, employed at this moment as dischargevalves, produces the reverse rotation of the motor by way of the port8b. The pressure ensuring the reverse rotation is maintained and limitedby the back-pressure valve 47.

According to a modification of the invention, the pipe 49 may beconnected to the port 0 of the valve 42 instead of putting it incommunication with the safety valve 44. This connection is shown indotted lines by the pipe 49A in FIG. 4.

Under these conditions. actuation of the three-way valve 48interconnects through its ports b and c the delivery circuit of the pump30 and the outlet 8b of the hydraulic motor 8. By manually releasing thebrake band 13 by means of the cylinder device 51, the residual pressureat the safety valve 45, employed at this moment as a discharge valve,produces the reverse rotation of the motor by way of the port 8b. Thepressure ensuring the reverse rotation is maintained andlimited by theback-pressure valve 47.

In order to once more effect the boring with the load falling freely,the three-way valve 48 must be returned to its initial position(intercommunication of the ports a and b).

Having now described our invention what we claim as new and desired tosecure by Letters Patent is:

l. A winch for hoisting a load and allowing the load to fall freely,comprising a support, a drum which is rotatably mounted relative to thesupport, a traction cable wound round the drum for attaching to theload, a hydraulic drive motor permanently coupled to said drum forrotating the drum and comprising first and second main fluid pressureports, a control fluid pressure port, a stator and a rotor, said winchfurther comprising a fluid supply device having pump means, a tank and acontrol device for selectively connecting said main fluid pressure portsto said pump means and said tank, said control device comprising firstpipe means connecting said second main fluid pressure port to said tankand second pipe means connecting said first pipe means to said controlfluid pressure inlet port for continuously applying thereto a controlfluid pressure, whereby upon actuation of said control device, saidrotor is drivable by application of main fluid pressure to said firstinlet port and capable of rotating freely with respect to said statorfrom the moment of release of said control device by virtue of controlfluid pressure remaining in said second pipe means.

2. A winch as claimed in claim 1, wherein said control device comprisesan accumulator connected to said second pipe means for providing thevolume of fluid required by said motor when said rotor passes from itsdriven state to its freely rotating state.

3. A winch as claimed in claim 2, wherein said control device furthercomprises a restriction and a check valve connected between said firstand second pipe means.

4. A winch as claimed in claim 1, comprising a calibrated valveconnected between said second pipe means and said tank for determiningthe maximum value of the control fluid pressure prevailing in saidsecond pipe means.

5. A winch as claimed in claim 1, further comprising a brake device forexerting a force for selectively braking and stopping rotation of thedrum, said brake device comprising a first hydraulic cylinder device forprogressively de-activating said brake device, said first hydrauliccylinder device being connected to said second pipe means so as to becontinuously supplied with hydraulic fluid from said second pipe means.

6. A winch as claimed in claim 5, wherein said brake device comprises abrake member combined with said drum so as to be capable of braking andstopping the latter, resiliently yieldable means for biasing the brakemember against the drum, a second hydraulic cylinder device forreleasing the brake member and a selector connected to said first andsecond hydraulic cylinder devices and to said first main fluid pressureport of said motor and being so arranged as to selectively apply fluidpressure to said second hydraulic cylinder device or to said first mainfluid pressure port depending respectively upon'whether said firsthydraulic cylinder device or said control device is actuated.

7. A winch as claimed inclaim 3, wherein said: control device comprisesan accumulator connected to said second pipe'means for providing thevolume of fluid required by said motor when said rotor passes fromits'driven state to its freely rotating state.

8. A winch as claimed in claim 7, wherein said control device furthercomprises a restriction and a check valve connected between said firstand second pipe means.

9. A winch as claimed in claim 5, wherein said control device comprisessafety valve means connected to said pump means and to said tank forselectively shortcircuiting said pump means, said safety valve meansbeing connected to said first hydraulic cylinder device so as to beactuated upon actuation of said first hydraulic cylinder device.

10. A winch as claimed in claim 1, comprising third pipe meansconnecting said main fluid pressure ports of said motor to each other,and a check valve connected in said third pipe means for isolating saidports when said motor is in the hoisting mode of operation by actuationof said control device.

1 1. A winch as claimed in claim 1, wherein said pump means comprises ahigh-flow pump and a low'flow pump, said control device comprising twocontrol directional valves respectively connecting the high-flow pumpand the low-flow pump to said motor.

12. A winch as claimed in claim 11, further comprising a brake devicefor exerting a force for selectively braking and stopping rotation ofthe drum, said brake device comprising a first hydraulic cylinder devicefor progressively de-activating said brake device, said first hydrauliccylinder device being connected to said second pipe means so as to becontinuously supplied with hydraulic fluid from said second pipe means,said control means further comprising two safety valves connectedrespectively to each of said pumps and to said first pipe means forselectively short-circuiting said pumps, a piloted check valve and anauxiliary check valve, said safety valves being connected to said firsthydraulic cylinder device through said piloted check valve which isdirectly connected to the safety valve associated with said low-flowpump and connected to the other safety valve associated with saidhigh-flow pump through said auxiliary check valve, whereby said safetyvalves are actuated upon actuation of said first hydraulic cylinderdevice.

13. A winch as claimed in claim 12, wherein the connection between saidhigh-flow pump and its associated safety valve comprises a branch pipemeans connected to a three-way valve so arranged as to be selectivelycapable to apply residual pressure generated at said safety valve byvirtue of shortcircuiting of said high-flow pump, to said second mainfluid pressure port of said motor for ensuring inverse rotation of thelatter.

14. A winch as claimed in claim 12, comprising a pipe for seriesconnecting said two control directional valves and a branch connectionon said pipe, said branch connection being connected to a three-wayvalve so arranged as to be selectively capable to apply a slight fluidpressure to said second main fluid pressure port of said motor forensuring inverse rotation of the latter.

15. A winch as claimed in claim 11, wherein said two control directionalvalves are connected in series.

16. A winch for hoisting a load and allowing the load to fall freely,comprising a support, a drum which is rotatably mounted relative to thesupport, a traction 'cable wound round the drum for attaching to theload,

a hydraulic drive motor permanently coupled to said drum for rotatingthe drum and comprising first and second main fluid pressure ports, acontrol fluid pressure port, a stator and a rotor, said winch furthercomprising a supply device having a high-flow pump, a lowflow pump, atank and control device, said control device comprising series connectedcontrol directional valves respectively connecting the high-flow pumpand the low-flow pump to said motor, first pipe means connecting saidsecond main fluid pressure port to said tank and second pipe meansconnecting said first pipe means to said control fluid pressure inletport, an accumulator connected to said second pipe means, safety valvesconnected respectively to each of said pumps and to said first pipemeans for selectively shortcircuiting said pumps, said winch furthercomprising a brake member resiliently biased against said drum, a brakerelease cylinder for releasing said brake member from said drum and apilot cylinder selectively connected to said brake release cylinder forprogressively actuating the latter and permanently connected to said

1. A winch for hoisting a load and allowing the load to fall freely,comprising a support, a drum which is rotatably mounted relative to thesupport, a traction cable wound round the drum for attaching to theload, a hydraulic drive motor permanently coupled to said drum forrotating the drum and comprising first and second main fluid pressureports, a control fluid pressure port, a stator and a rotor, said winchfurther comprising a fluid supply device having pump means, a tank and acontrol device for selectively connecting said main fluid pressure portsto said pump means and said tank, said control device comprising firstpipe means connecting said second main fluid pressure port to said tankand second pipe means connecting said first pipe means to said controlfluid pressure inlet port for continuously applying thereto a controlfluid pressure, whereby upon actuation of said control device, saidrotor is drivable by application of main fluid pressure to said firstinlet port and capable of rotating freely with respect to said statorfrom the moment of release of said control device by virtue of controlfluid pressure remaining in said second pipe means.
 2. A winch asclaimed in claim 1, wherein said control device comprises an accumulatorconnected to said second pipe means for providing the volume of fluidrequired by said motor when said rotor passes from its driven state toits freely rotating state.
 3. A winch as claimed in claim 2, whereinsaid control device further comprises a restriction and a check valveconnected between said first and second pipe means.
 4. A winch asclaimed in claim 1, comprising a calibrated valve connected between saidsecond pipe means and said tank for determining the maximum value of thecontrol fluid pressure prevailing in said second pipe means.
 5. A winchas claimed in claim 1, further comprising a brake device for exerting aforce for selectively braking and stopping rotation of the drum, saidbrake device comprising a first hydraulic cylinder device forprogressively de-activating said brake device, said first hydrauliccylinder device being connected to said second pipe means so as to becontinuously supplied with hydraulic fluid from said second pipe means.6. A winch as claimed in claim 5, wherein said brake device comprises abrake member combined with said drum so as to be capable of braking andstopping the latter, resiliently yieldable means for biasing the brakemember against the drum, a second hydraulic cylinder device forreleasing the brake member and a selector connected to said first andsecond hydraulic cylinder devices and to said first main fluid pressureport of said motor and being so arranged as to selectively apply fluidpressure to said second hydraulic cylinder device or to saId first mainfluid pressure port depending respectively upon whether said firsthydraulic cylinder device or said control device is actuated.
 7. A winchas claimed in claim 3, wherein said control device comprises anaccumulator connected to said second pipe means for providing the volumeof fluid required by said motor when said rotor passes from its drivenstate to its freely rotating state.
 8. A winch as claimed in claim 7,wherein said control device further comprises a restriction and a checkvalve connected between said first and second pipe means.
 9. A winch asclaimed in claim 5, wherein said control device comprises safety valvemeans connected to said pump means and to said tank for selectivelyshort-circuiting said pump means, said safety valve means beingconnected to said first hydraulic cylinder device so as to be actuatedupon actuation of said first hydraulic cylinder device.
 10. A winch asclaimed in claim 1, comprising third pipe means connecting said mainfluid pressure ports of said motor to each other, and a check valveconnected in said third pipe means for isolating said ports when saidmotor is in the hoisting mode of operation by actuation of said controldevice.
 11. A winch as claimed in claim 1, wherein said pump meanscomprises a high-flow pump and a low-flow pump, said control devicecomprising two control directional valves respectively connecting thehigh-flow pump and the low-flow pump to said motor.
 12. A winch asclaimed in claim 11, further comprising a brake device for exerting aforce for selectively braking and stopping rotation of the drum, saidbrake device comprising a first hydraulic cylinder device forprogressively de-activating said brake device, said first hydrauliccylinder device being connected to said second pipe means so as to becontinuously supplied with hydraulic fluid from said second pipe means,said control means further comprising two safety valves connectedrespectively to each of said pumps and to said first pipe means forselectively short-circuiting said pumps, a piloted check valve and anauxiliary check valve, said safety valves being connected to said firsthydraulic cylinder device through said piloted check valve which isdirectly connected to the safety valve associated with said low-flowpump and connected to the other safety valve associated with saidhigh-flow pump through said auxiliary check valve, whereby said safetyvalves are actuated upon actuation of said first hydraulic cylinderdevice.
 13. A winch as claimed in claim 12, wherein the connectionbetween said high-flow pump and its associated safety valve comprises abranch pipe means connected to a three-way valve so arranged as to beselectively capable to apply residual pressure generated at said safetyvalve by virtue of short-circuiting of said high-flow pump, to saidsecond main fluid pressure port of said motor for ensuring inverserotation of the latter.
 14. A winch as claimed in claim 12, comprising apipe for series connecting said two control directional valves and abranch connection on said pipe, said branch connection being connectedto a three-way valve so arranged as to be selectively capable to apply aslight fluid pressure to said second main fluid pressure port of saidmotor for ensuring inverse rotation of the latter.
 15. A winch asclaimed in claim 11, wherein said two control directional valves areconnected in series.
 16. A winch for hoisting a load and allowing theload to fall freely, comprising a support, a drum which is rotatablymounted relative to the support, a traction cable wound round the drumfor attaching to the load, a hydraulic drive motor permanently coupledto said drum for rotating the drum and comprising first and second mainfluid pressure ports, a control fluid pressure port, a stator and arotor, said winch further comprising a supply device having a high-flowpump, a low-flow pump, a tank and control device, said control devicecomprising series connected control direCtional valves respectivelyconnecting the high-flow pump and the low-flow pump to said motor, firstpipe means connecting said second main fluid pressure port to said tankand second pipe means connecting said first pipe means to said controlfluid pressure inlet port, an accumulator connected to said second pipemeans, safety valves connected respectively to each of said pumps and tosaid first pipe means for selectively short-circuiting said pumps, saidwinch further comprising a brake member resiliently biased against saiddrum, a brake release cylinder for releasing said brake member from saiddrum and a pilot cylinder selectively connected to said brake releasecylinder for progressively actuating the latter and permanentlyconnected to said second pipe means and to each of said safety valves.